Cordless clock of commercial powerferquency synchronized type



Jan. 5, 1965 w. KOHLHAGEN CORDLESS cLocK oF COMMERCIAL POWER-FREQUENCY sYNcHRoNIzED TYPE Filed Jan. 29, 1962 INV EN TOR United States Patent 3,l63,978 CRIULESS (1L/UCK 0F QGMMERCIAL POWER- FFJEQUENCY SYNCHRNZED TYPE Walter Kohlhagen, 818 Oakley Ave., Elgin, Ill. Filed Jan. 29, 1962;, Ser. No. 169,394 5 Claims. (Cl. 58--Z3) This invention relates to cordless timekeeping devices in general, and to cordless clocks of power-frequency synchronized type in particular.

Clocks of this type are known, and their most distinguishing characteristic is that their operation as well as their synchronization with the commercial frequency of an ordinary alternating current distribution system nearby, such as a household power line, is achieved without any physical connection with the current distribution system. There is thus eliminated in clocks of this type the usual cords and their mostly unsightly extension to the nearest outlets, and the clocks may also be located in places best suited or desired for them without any concern of reaching the nearest outlets with the clock cords. To the end of achieving operation and synchronization of such a clock, it is provided with a commercial frequency pick-up device and an amplier for amplification of power of ordinary commercial frequency. The pickup device responds to the electric or magnetic induction field of commercial frequency in the space within or about the clock whenever the latter is within such distances of an energized commercial power line as are commonly involved in ordinary household or other indoor use of the clock, and supplies to the amplifier voltage of the power line frequency for amplification. The voltage thus amplified is supplied to the` clock motor for operation of the clock in synchronism with the commercial frequency, with the clock motor being of conventional synchronous type.

While these prior clocks perform quite satisfactorily, the requirement that the amplified voltage must be adequate to run the clocks presents certain drawbacks. Thus, despite the fact that the amplifier circuits of these clocks are kept as simple as possible, being mostly batterypowered transistor amplifiers to that end, the required operating voltage involves nevertheless quite considerable amplification of the voltage supplied by the pick-up devices, which necessarily entails considerable cost. To further meet the requirement of adequate operating vol*- age from the amplifiers of reasonable simplicity, their pick-up devices must be in a relatively strong induction field in space which may well lack the necessary strength in some desirable locations and thus impose limitations on the clocks in this respect. Further, these clocks require quite accurate and efficient and, hence, relat-ively costly synchronous motors in order to perform reliably with `the available voltage from the amplifiers. All in all, these drawbacks in particular and still others, all springing from the drive of the clocks by the voltage from their amplifiers, have priced these clocks beyond reach of most and also account for the fact that they failed to become a popular item with the public at large.

It is an object of the present invention to provide a cordless clock of this type which is considerably simpler in construction and, hence, of considerably lower cost than prior clocks of this type, yet performs in general at least as reliably as the latter.

It is another object of the present invention to provide a cordless clock of this type which despite its aforementioned simpler construction and lower cost, even in the matter of the amplifier, will perform reliablyin an induction field in space within a much wider range of field intensities, including exceedingly weak intensities, than the range of relatively strong field intensities in which the prior clocks will reliably perform.

ICC

Another object of the present inventionI is to provide cordless clock of this type in which the driving power is derived from any suitable non-synchronous electric or non-electric motor, and preferably from an exceedingly simple D.C. motor that may advantageously be powered from a long-life battery, and the frequency-regulated voltage from an amplifier need merely be applied to brake the motor and permit its runaway in synchronism with the regulated frequency. In so doing, the drive component of the clock is of the utmost simplicity and is incomparably simpler than those of the prior clocks, and the voltage from the amplifier required for the specified purpose is exceedingly small so that the amplifier may have an extremely wide range of effective pick-up and the voltage supplied to the amplifier by the pick-up in even the Weakest induction field in the surrounding space requires but a minimum of amplification and, hence, an amplifier of exceeding simplicity and low cost.

It is a further object of the present invention to provide a cordless clock of this type in which the voltage from the amplifier is used to operate a magnetic escapement for the D.C. powered clock drive, with the escapement being advantageously in the general structural form of a synchronous reaction motor with a field and a permarient magnet rotor, but applied as a brake by connecting the rotor with the clock drive and thus making it the runaway member of the escapement, and supplying the voltage of power line frequency from the amplifier to the coil of the fixed field. Thus, the escapement has only one movable part which, moreover, is constantly driven, and the escapement requires for its operation exceedingly small power owing to the fact that it has to overpower but that small part of the output torque of the D,C. motor which is in excess of that required for running the clock, wherefore this synchronous motor type brake may be of optimum structural simplicity and, hence, exceedingly low cost, yet will perform accurately and reliably despite even the widest tolerances in the coordination of the field poles with each other and with the rotor. Furthermore, owing to the very small power required by the escapement for its reliable operation, it is well within the capacity of the escapement to perform reliably at even wide voltage changes in the nearby power distribution system.

Another object of the present invention is to provide a cordless clock of this type the motor-powered drive of which may be synchronized with a synchronous motor type brake that may be operated, alternatively, by a pulsating D.C. output from the amplifier without any need for an output transformer. This yis entirely feasible in view of the fact that this brake requires for its operation as little power as the aforementioned brake, and the same is structurally also as simple as the latter, merely requiring in lieu of a permanent-magnet rotor a ferrous rotor with shaped pole teeth and in lieu of a number of field poles of field-flux induced alternating polarities field poles of permanent polarity.

A further object of the present invention is to provide a cordless clock of this type in which the rotor of either. of the aforementioned alternative synchronous motor type brakes is preferably connected with the fastest running element of the clock drive through intermediation of speed reduction gearing such that the rotor is the fastest running element of the clock, thereby to keep the power requirement of the brake for its operation particularly low.

It is another object of the present invention to provide a cordless clock of this type in which the rotor of either of the alternative synchronous motor type brakes is connected through speed reduction gearing with the fastest running element of the clock drive as aforementioned, with this fas-test element of the clock drive being the shaft of the drive motor which through other speed reduction gearing is connected with the second fastest running element of the clock drive, namely the sweep-second shaft. With this arrangement, the torque required from the drive motor for running the clock is especially low, and this low torque requirement of the motor is reiiected in still lower power requirement of the brake for its operation.

Other objects and advantages will appear to those skilled in the art from the following, considered in conjunction with the accompanying drawings.

In the accompanying drawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

FIG. l is a view, partly in section and partly diagrammatic, of an exemplary clock embodying the present invention;

FIGS. 2 and 3 are fragmentary diagrammatic views of modified components of the same clock;

FIG. 4 is a view of a prominent operating device of the clock;

FIG. 5 is a section taken on the line 5-5 of FIG. 4;

FIG. 6 is a View of a modified operating device of the clock;

FIG. 7 is a section taken on the line 7-7 of FIG. 6;

FIG. 8 is a view of a further modified operating device of the clock; and

FIG. 9 is a section taken on the line 9 9 of FIG. 8.-

Referring to the drawings, and more particularly to FIG. 1 thereof, the reference numeral 10 designates a timekeeping device which in the present instance is a clock with a movement 12 having a prime mover 14 and a gear train 16 for operating the hour, minute and sweep-second shafts 18, 20 and 22, respectively. The prime mover 14 may be any suitable non-synchronous electric or non-electric motor, and is preferably a simple low-cost D.C. motor powered from any suitable D.C. source, such as the battery 24. Accordingly, since the motor 14 is non-synchronous and of runaway type, the movement 12 includes an escapement 26 to control the drive of the motor 14 for proper timekeeping purposes.

The motor 14 is in this instance carried in back of pillar-spaced movement plates 2S and 30, and the hour, minute and sweep-second shafts 1S, 2t) and 22 are nested together in conventional manner, with the minute shaft 20 turning on the sweep-second shaft 22 and the hour shaft 18 turning on the minute shaft 2i?. The shaft 32 of the motor 14 is in this instance drivingly connected with the sweep-second shaft 22 by a first speed-reduction stage of the gear train 16 which comprises a pinion 34 on the motor shaft 32 and a meshing gear 36 on the sweep-second shaft 22 between the plates 28 and 3). Interposed between the sweep-second shaft 22 and minute shaft 2) is a second reduction stage of the gear train 16 for the correct drive of the minute shaft from the sweepsecond shaft, this stage comprising pairs of meshing pinions and gears 38, tti and 42, 44 of which pinion S turns with the gear 36 on the sweep-second shaft 22, gear 40 and pinion 42 are fast on a rotary staff 46 between the plates 28 and 30, and gear 44 is carried by the minute shaft 20. interposed between the minute s haft 2t) and hour shaft 18 is still another reduction stage of the gear train 16 for the correct drive of the hour shaft from the minute shaft, this stage comprisino two pairs of meshing pinions and gears 48, 59 and 52, 54 of which pinion 4S turns with the gear 44 on the `minute shaft 2t), gear 50 and pinion 52 are fast on a rotary stati 56 between the plates 28 and 30, and gear 54 is carried by the hour shaft 18.

The escapement 26, which is shown diagranrniatically in FIG. 1, is of magnetic type and has a rotor et) on a shaft 61 and a fixed ield structure 62, of which the rotor is drivingly connected with the clock drive, and in this instance with the shaft 32 of the motor 14. Preferably, and for reasons explained hereinafter, the rotor 6) is connected with the motor shaft 32 through reducion gearing 63 comprising two pairs of meshing pinions and gears 64, ed and 68, '76 of which pinion 64 is carried by the rotor shaft 61, gear 65 and pinion 6d are fast on a rotary staff 72 between the plates 2S and 3i), and gear 76 is fast on the motor shaft 32.

In operation of the clock, the motor 14 drives the time shafts 18, 2t? and 22 through intermediation of the gear train 16, and the motor 14 also drives the rotor 60 of the escapement 26 which in a manner described hereinafter permits the escape of the motor-driven rotor at the correct rate at which the sweep-second, minute and hour shafts 22, 2th and 18 will be driven at the usual rates of one revolution per minute, one revolution per hour and one revolution per twelve hours, respectively.

The exemplary escapement 26, which is shown in detail in FIGS. 4 and 5, is structurally like a synchronous reaction motor, with the rotor 69 being of permanent-magnet type and having pole faces 74 and 76 of the indicated exemplary permanent polarities, and the field 62 having two sets of field poles 78 and Si), and a field coil S2. The poles '73 are formed on one field plate S4 and the poles 80 are formed on another field plate 36, with both field plates S4 and 85 being connected by a magnetic center core 33 which provides a preferably lubricated bearing (not shown) for the rotor shaft 61. The field coil 82 surrounds the core Sh and is interposed between the field plates 84 and 8d in conventional manner. The eld poles 78 and Si? are arranged circularly about the rotor axis x, and successive 4poles of either set 78 or 80 alternate in this instance with successive field poles of the other set. Also, the field poles 73 and Sti are in this instance equal in number to the pole faces 74 and 76 of the rotor 60. The escapement 26 may be mounted with its iield plate 86 on the front movement plate 28 (FIG. l).

Assuming that the escapement 26 were disconnected from the clock drive, the escapement would on energization of the field coil 32 perform like a synchronous motor. Thus, on supplying the field coil 82 with alternating current, there will be produced in the field poles 78 and 86 instantaneous opposite polarities, respectively, which change with the alternation of the current, and the rotor 60 would step in either direction in phase with the current. In the performance of the escapement 26 as such, the rotor oil steps in the direction dictated by the clock drive and in phase with the supplied alternating current and, hence, in synchronism with the frequency of the current, but the field 62 acts as a brake on the motor-driven rotor 6i) to hold its runaway speed and, hence thatof the clock drive in synchronism with the current frequency. To do so, the running torque of the escapement 26, being in this instance brake torque rather than driving torque in its effect on the rotor et), need merely be in excess of the torque of the rotor 60, and since the motor 14 may readily be of such capacity that its output torque is only reasonably in excess of that required for the clock drive, it stands to reason that the running torque of the escapement may indeed be quite small.

This requirement of low operating torque of the escapement 26 is highly advantageous. Thus, the escapement will perform quite reliably despite even Wide tolerances in the coordination of the field poles 78, Sil with each other as well as with the rotor 60, and the rotor may also be of most any low-cost permanent-magnet material. Also, since the drive direction of the rotor is dictated by the clock drive, the present escapment requires no provisions for unidirectional start and drive of its rotor. Accordingly, the escapement readily lends itself to efficient mass production at particularly low cost. Furthermore, due to the required low operating torque of the escapement, the same will perform reliably within an exceedingly wide voltage range, and even at exceedingly low voltages of the applied current, and this assumes particular significance as explained hereinafter.

In the present exemplary clock, the brake torque of the escapement 26 may be particularly low since the rotor 60 lis the fastest driven element of the clock, its speed being in the present example stepped up from that of the rotor shaft 32 at the ratio of 50 to 1 by the gearing 63. Thus, assuming that the frequency of the current supplied to the field coil 82 is 60 cycle, as is usual in the United States, and with the field poles 78 and 80 numbering twenty in this instance (FIG. 4), the rotor 60 will have an escape rate of 180 r.p.m., while the motor shaft 32 will at the aforementioned 50 to 1 ratio have an escape of 3 rpm. This entirely practical example serves to demonstrate particularly well that the brake torque of the escapement 26 may be indeed be exceedingly small in order to keep the clock drive in synchronism with the frequency of the current supplied to the field coil 82. The required brake torque of the escapement 26 for keeping the clock drive in synchronism with the frequency of the current supplied to the field coil 82 is particularly low in the present exemplary clock since the motor 14 -is drivingly connected with the sweep-second shaft 22, not directly but through intermediation of the described first reduction stage 34, 36 of the gear train 16, which further reduces the torque requirement of theL motor 14 for the drive of the clock. In the present example, the speeds of the motor shaft 32 and sweepsecond shaft 22 are at the ratio of 3 to 1 at the aforementioned exemplary synchronous speed of the motor shaft 32 of 3 r.p.m.

In accordance with another important aspect of the present invention, the clock is provided with a commercial frequency pick-up device or field-sensing element and an amplifier for amplification of power of ordinary commercial frequency. The sensing element responds to the induction field of commercial frequency in space within or without the clock whenever the clock is within such distances of a commercial power line as are involved in household or other indoor use of the clock, and supplies to the amplifier for amplification voltage of the power line frequency. The amplified voltage is supplied to the field coil 82 of the escapement 26 for operation of the latter.

The held-sensing element and the amplifier with the field coil 82 in the output stage thereof are shown in a circuit diagram in FIG. 1, it being understood that the amplifier is preferably located in the clockcase (not shown) while the field-sensing element may be located within or without the clockcase. The field-sensing element is, in the present instance, a preferably ferrite-cored pick-up coil 90 which is sensitive to the magnetic induction field established by a nearby power distribution system, such as a commercial power line in a wall, for example, of a room in which the clock is present. As long as the clock with its pick-up coil 90 is in this magnetic induction field, there will be generated in this coil 90 a voltage of the frequency of the power distribution system. This generated voltage is, of course, much too small for operation of the escapement 26 despite its exceedingly low operating torque requirements, wherefore this voltage, or current, is amplified in the amplifier 92 which in the present instance \is of battery-powered transistor type and has two amplifier Stages 94 and 96. The current of commercial frequency generated in the coil 90 is thus amplified by the first amplifier stage 94, which comprises a transistor 98 with the base 100, emitter 102 and collector 104, the bias resistors 106, 108 and 110, a bypass condenser 112 and a fixed turning condenser 114. The current generated in the coil 90 is applied between the base 100 and emitter 102 of the transistor 98 by leads 101 and 103, and the transistor amplifies this current, with the amplified output from the collector 104 thereof being applied to the primary coil 116 of an interstage coupling transformer 118. For the amplification of the generated current, the battery 120 supplies the necessary currents and voltages, and the resistors 106, 108 and 110 establish the proper bias voltages at the base and emitter 102 of the transistor 9S, while the bypass condenser 112 applies the generated current to the emitter 102 of the transistor 08. The amplified current of commercial frequency induced in the secondary coil 122 of the interstage coupling transformer 11S is further amplified in the second amplifier stage 96, which in this instance comprises a transistor 124 with a base 126, emitter 128 and collector 130, thebias resistors 132, 134 and 136, and a bypass condenser 138. The current induced in the secondary coil 122 of transformer 118 is applied between the base 126 and emitter 128 of the transistor 124 by leads 140 and 142, with the amplified output from the collector 130 being applied to the primary coil 144 of an output transformer 146. For the current amplification in this second stage 96, the resistors 132, 134, 136 and the bypass condenser 130 perform the same functions as their respective counterparts 106, 108, and 112 of the first amplifier stage 94. The further amplified current of commercial frequency induced in the secondary coil 148 of the output condenser 146 is supplied to the field coil 82 of the escapement 26.

The described exemplary amplifier 92 may be entirely conventional, and any other suitable amplifier may be used in lieu thereof. However, regardless of the type of amplifier that may be used, the same may be simple and, hence, of very low cost, with the required overall amplification of the current generated in the pick-up coil 90 being relatively low for operation of the escapement 26. Thus, the present exemplary two amplifier stages will in most cases be more than adequate for supplying the field coil 82 with the requisite current for the reliable operation of the escapement 26, this in view of the fact that the escapement requires exceedingly low power for its operation, as explained. Also, in view of the exceedingly low power requirement of the escapement 26 for its reliable operation, the amplifier will supply to the field coil 82 adequate current for the purpose even if the signal received by the pick-up coil 90 from the surrounding induction field should be exceedingly weak, and even much weaker than the signal of minimum intensity which on even higher amplification in prior clocks would barely be adequate for operating their synchronous drive motors. Accordingly, the present clock will perform reliably in an induction field of most any strength, including the lowest, wherefore the clock will perform at most any distance from the nearest power distribution system, including distances at which the prior clocks would not perform. The pick-up range of the sensing element is thus extremely wide. Also, in view of the low power requirement, and hence also low current requirement, of the escapement 26 for its operation, the same will perform at most any voltage changes in the power distribution system, including the lowest voltages at which the prior clocks would fail to operate.

The strength of the magnetic induction field surrounding the pick-up coil 90 is determined by the magnitude of the load current in the near by power distribution system, and if no current is caused to fiow in the distribution system the field will disappear and the clock will fail in consequence. However, todays numerous electrical appliances in household and other indoor use would most likely cause a load current to be constantly drawn through the power distribution system in the magnetic induction field of which the clock would be placed so that the clock would never fail. In this connection, the low current requirement of the escapement 26 is also particularly advantageous because the amplifier would respond to even the weakest signal from the induction field and supply adequate operating current to the field coil 82 of the escapement.

Further in view of the low power requirement of the escapement 26, the number of its field poles may be less than the number of pole faces of its rotor, or vice versa, and the escapement may structurally be further simplified. Such a simplified escapement is shown at 26a in FIGS. 6 and 7, the same having a rotor 60a which in this instance is identical with the rotor 60 of FIGS. 4 and 5, but the field 62a is different and simplified. Thus, the field plates 84a and 86a have only a few, presently four, field poles 78a and Stia, respectively, which are arranged on opposite sides of the rotor axis xa. With the field coil 82a surrounding the center core 88a and being interposed between the field plates 84a and 36a, the field poles 78a and 39a will, on energization of the field coil 82a, have instantaneous opposite polarities, respectively, which change with the alternation of the current supplied to the field coil, with the rotor 60a stepping in synchronism with the frequency of this current. Thus, while the present escapement 26a is structurally simpler and necessarily produces less power than the escapernent 26 of FIGS. 4 and 5, its power output is nevertheless quite adequate for synchronization of the clock drive with the frequency of a nearby power distribution system.

Reference is now had to FIG. 3 which shows a capacitive pick-up device 160 for the amplifier of FIG. 1. This capacitive pick-up device is sensitive to the surrounding electric field produced by the nearby power distribution system, with the advantage that the strength of the signal received by the pick-up device does not vary with varying amounts of load current in the nearby power distribution system since the electric field will be substantially unaffected by such varying amounts of load current. The capacitive pick-up device 160 comprises in this instance two plates 162 and 164 and a parallel tuned circuit comprised of a coil 166 and a condenser 168 which is tuned to the frequency of the nearby power distribution system, with the pick-up device being connected with the exemplary amplifier of FIG. l as indicated by like referenced components thereof in FIG. 3.

The cloc.; of FIG. l may also be controlled by a magnetic escapement 17d (FIG. 2) which is operated by pulsating D.C. current, with the current pulsating at the frequency of a nearby power distribution system. To this end, the amplifier 92 of FlG. l may be used with the magnetic pick-up device Sill r the capacitive pick-up device 16@ of FIG. 3, with the amplifier being modified, however, so that the final transistor amplification stage thereof is operated as a class B amplifier. To this end, there is substituted for the output transformer 146 and field coil 82 in FIG. 1 an output coil 172 which is the field coil of the escapement 17@ (FIG. 2).

The escapement 17@ may be of the exemplary form shown in FIGS. 8 and 9, comprising a rotor 174 and a field structure 176 with the field coil 172. The rotor 174 is of ferrous material and has shaped pole teeth 178 which in this instance number twenty, the same as the pole faces of the described permanent-magnet rotor 6@ of FIG. 4. The field structure 176 has two sets of field poles 18@ and 162 of flux-induced polarities and a set of field poles 18d of permanent polarities, of which the poles 1S@ and 132. are formed by field plates 186 and 188, respectively, that are connected by a magnetic center core 19t?. The field poles 11i@ and 1&2 are only a few in number, in this instance four each, and they are arranged on opposite sides of the rotor axis y and in this instance spaced at the pitch of the rotor teeth 178. The field poles 136 and 182 are further arranged so that all may simultaneously be in alignment with adjacent rotor teeth 178. The field poles 154 of permanent polarities are permarient magnets in a magnetic member 192 on a nonmagnetic plate 194 that may suitably be secured to the field plate 18e. The field poles 184- are fewer in number than the combined field poles 1fi and 182, and number four in this instance, and they are spaced apart at the pitch of the rotor teeth 173. Furthermore, the field poles 184 are arranged so as to be in alignment with adjacent rotor kteeth 178 when the other field poles 181i and 132 are out of alignment with adjacent rotor teeth (FIG. 8).

In operation of the escapement 170, the rotor 174 is driven by the clock drive and its runaway speed is in synchronism with the frequency of the nearby power distribution system. To this end, the rotor 174 steps with its teeth 178 alternately into alignment with the field poles 13d, 132 and with the field poles 184. In this connection, the pulsating DC. current in the field coil 172 will produce always the same polarities in the field poles 18) and 182, with those of the field poles 180 being opposite to those of the other field poles 182 in the exemplary manner indicated. Thus, assuming the drive direction of the rotor 174 to be clockwise in FIG. 8 and the permanent polarities of the held poles 184 toy be as indicated, the rotor 174 has just been permitted to escape with its teeth 178 into alignment and, hence, magnetic coupling relation with the field poles 184 which restrain the rotor against further clockwise drive until the next pulse in the field coil 172 produces the indicated polarities in the field poles 18) and 132. When this occurs, the field poles 181i and 1&2 combine to force the rotor 174 with its teeth 178 clockwise from alignment with the field poles 184 and to restrain further clockwise escape of the rotor when the very next rotor teeth align with the field poles 139 and 182. As the pulse in the field coil 172 disappears, the field poles are momentarily without elective polarity and the rotor will be permitted to escape clockwise until its teeth next align with the field poles 1114 `of permanent polarity. The rotor 174 thus steps with its teeth 17S alternately into alignment with the field poles 180, 132 and with the field poles 184 in synchronism with `the frequency of the pulsating D.C. current from the amplifier and, hence, in synchronism with the frequency of the nearby power distribution system.

The invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced there- 1n.

What is claimed is:

l. In a clock, the combination with a movement, of a non-synchronous motor connected with said movement for operating the same, but at excessive speed; and a device for synchronizing said motor with the frequency of a power distribution system nearby without electrical circuit connection therewith, said device comprising an escapement having a permanent-magnet rotor with pole faces and an associated multi-polar field with a coil in flux-inducing relation therewith, of which said rotor is drivingly connected with said motor, and power amplifying means and associated field sensing means for arnplifying electromotive force of the frequency of and produced by said distribution means and picked up from the field in space by said sensing means in said field, with said coil being supplied with said amplied electromotive force, and said escapement acting as a self-energized generator and exerting a braking force which is the product of the permanent and induced magnetic forces in the escapement, thereby requiring minimum power amplification.

2. The combination in a clock as set forth in claim 1, in which said field has two sets of field poles arranged circularly about said rotor of which successive poles of either set alternate with successive poles of the other set, said coil produces in said pole sets opposite polarities, respectively, changing with the alternation of said amplified electromotive force, and said rotor poles and eld poles cooperate to keep the motor-drive of said rotor in synchronism with the frequency of said amplified electromotive force.

3. The combination in a clock as set forth in claim 1, in which said field has two sets of field poles arranged circularly about said rotor of which ythe poles of each set are successive with each other, said coil produces in said pole sets opposite polarities, respectively, changing with the alternation of said amplified eleotromotive force, and Said rotor poles and eld poles cooperate to keep rthe motor-drive of said rotor in synchronism with the frequency of said amplified electrom-otive force.

4. The combination in a clock as set forth in claim 1, which further comprises reduction gearing for driving said rotor from said motor at a speed which is a multiple of the moto-r speed.

5. The combination in a clock as set forth in claim 1, in which said movement includes a sweep-second shaft, and there is further provided reduction gearing for driving said rotor from said motor at a speed which is a multiple of the motor speed, and other reduction gearing between said motor and shaft for the drive of said shaft at a yfraction of the motor speed.

References Cited in the file of this patent UNITED STATES PATENTS Cooley Dec. 17, Clokey Apr. 8, Von Arco ug. 5, Horni Aug. 11, Kohlhagen May 4, Ryan June 12, Williams Nov. 26, Boyles Aug. 8, Hermann et al. Sept. 19, Kohlhagen Dec. 11,

FOREIGN PATENTS France June 26,

OTHER REFERENCES The Problem of Synchronism in Television, Television, July 1928, pages 10, 11. 

1. IN A CLOCK, THE COMBINATION WITH A MOVEMENT, OF A NON-SYNCHRONOUS MOTOR CONNECTED WITH SAID MOVEMENT FOR OPERATING THE SAME, BUT AT EXCESSIVE SPEED; AND A DEVICE FOR SYNCHRONIZING SAID MOTOR WITH THE FREQUENCY OF A POWER DISTRIBUTION SYSTEM NEARBY WITHOUT ELECTRICAL CIRCUIT CONNECTION THEREWITH, SAID DEVICE COMPRISING AN EXCAPEMENT HAVING A PERMANENT-MAGNET ROTOR WITH POLE FACES AND AN ASSOCIATED MULTI-POLAR FIELD WITH A COIL IN FLUX-INDUCING RELATION THEREWITH, OF WHICH SAID ROTOR IS DRIVINGLY CONNECTED WITH SAID MOTOR, AND POWER AMPLIFYING MEANS AND ASSOCIATED FIELD SENSING MEANS FOR AMPLIFYING ELECTROMOTIVE FORCE OF THE FREQUENCY OF AND PRODUCED BY SAID DISTRIBUTION MEANS AND PICKED UP FROM THE FIELD IN SPACE BY SAID SENSING MEANS IN SAID FIELD, WITH SAID COIL BEING SUPPLIED WITH SAID AMPLIFIED ELECTROMOTIVE FORCE, AND SAID ESCAPEMENT ACTING AS A SELF-ENERGIZED GENERATOR AND EXERTING A BRAKING FORCE WHICH IS THE PRODUCT OF THE PERMANENT AND INDUCED MAGNETIC FORCES IN THE 